This study assesses the effects of subcutaneously administered r-metHuNT-3 (neurotrophin 3) on stool form and on gastrointestinal transit in normal healthy volunteers and in patients with idiopathic slow transit constipation over a 2-week period. NT-3 is a neurotrophic factor normally found in very small quantities in the brain, nerve, muscle, and gland cells of humans and has been studied in over 100 patients as a potential treatment for certain neurological diseases. This study evaluates its effects on digestive functions in detail.